* src/lalr.c (state_lookahead_tokens_count): Correct comment.

[bison.git] / src / lalr.c

diff --git a/src/lalr.c b/src/lalr.c
index 00455b06a9f63ddcd9662f49fc532f2b8baaa9c5..fbd2800f0529905c30cd990bf30480c1e1fb75ed 100644 (file)
--- a/src/lalr.c
+++ b/src/lalr.c
@@ -1,24 +1,22 @@
 /* Compute lookahead criteria for Bison.
 
    Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004, 2005,
 /* Compute lookahead criteria for Bison.
 
    Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004, 2005,

-   2006 Free Software Foundation, Inc.
+   2006, 2007, 2008, 2009 Free Software Foundation, Inc.

 
    This file is part of Bison, the GNU Compiler Compiler.
 
 
    This file is part of Bison, the GNU Compiler Compiler.
 

-   Bison is free software; you can redistribute it and/or modify
+   This program is free software: you can redistribute it and/or modify

    it under the terms of the GNU General Public License as published by
    it under the terms of the GNU General Public License as published by

-   the Free Software Foundation; either version 2, or (at your option)
-   any later version.
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.

 
 

-   Bison is distributed in the hope that it will be useful,
+   This program is distributed in the hope that it will be useful,

    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License

-   along with Bison; see the file COPYING.  If not, write to
-   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
-   Boston, MA 02110-1301, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

 
 
 /* Compute how to make the finite state machine deterministic; find
 
 
 /* Compute how to make the finite state machine deterministic; find


@@ -38,15 +36,17 @@
 #include "getargs.h"
 #include "gram.h"
 #include "lalr.h"
 #include "getargs.h"
 #include "gram.h"
 #include "lalr.h"

+#include "muscle-tab.h"

 #include "nullable.h"
 #include "reader.h"
 #include "relation.h"
 #include "symtab.h"
 
 goto_number *goto_map;
 #include "nullable.h"
 #include "reader.h"
 #include "relation.h"
 #include "symtab.h"
 
 goto_number *goto_map;

-static goto_number ngotos;
+goto_number ngotos;

 state_number *from_state;
 state_number *to_state;
 state_number *from_state;
 state_number *to_state;

+bitsetv goto_follows = NULL;

 
 /* Linked list of goto numbers.  */
 typedef struct goto_list
 
 /* Linked list of goto numbers.  */
 typedef struct goto_list


@@ -65,17 +65,13 @@ static bitsetv LA = NULL;
 size_t nLA;
 
 
 size_t nLA;
 
 

-/* And for the famous F variable, which name is so descriptive that a
-   comment is hardly needed.  <grin>.  */
-static bitsetv F = NULL;
-

 static goto_number **includes;
 static goto_list **lookback;
 
 
 
 
 static goto_number **includes;
 static goto_list **lookback;
 
 
 
 

-static void
+void

 set_goto_map (void)
 {
   state_number s;
 set_goto_map (void)
 {
   state_number s;


@@ -135,12 +131,7 @@ set_goto_map (void)
 }
 
 
 }
 
 

-
-/*----------------------------------------------------------.
-| Map a state/symbol pair into its numeric representation.  |
-`----------------------------------------------------------*/
-
-static goto_number
+goto_number

 map_goto (state_number s0, symbol_number sym)
 {
   goto_number high;
 map_goto (state_number s0, symbol_number sym)
 {
   goto_number high;


@@ -175,7 +166,7 @@ initialize_F (void)
 
   goto_number i;
 
 
   goto_number i;
 

-  F = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
+  goto_follows = bitsetv_create (ngotos, ntokens, BITSET_FIXED);

 
   for (i = 0; i < ngotos; i++)
     {
 
   for (i = 0; i < ngotos; i++)
     {


@@ -184,7 +175,7 @@ initialize_F (void)
 
       int j;
       FOR_EACH_SHIFT (sp, j)
 
       int j;
       FOR_EACH_SHIFT (sp, j)

-       bitset_set (F[i], TRANSITION_SYMBOL (sp, j));
+       bitset_set (goto_follows[i], TRANSITION_SYMBOL (sp, j));

 
       for (; j < sp->num; j++)
        {
 
       for (; j < sp->num; j++)
        {


@@ -204,7 +195,7 @@ initialize_F (void)
        }
     }
 
        }
     }
 

-  relation_digraph (reads, ngotos, &F);
+  relation_digraph (reads, ngotos, &goto_follows);

 
   for (i = 0; i < ngotos; i++)
     free (reads[i]);
 
   for (i = 0; i < ngotos; i++)
     free (reads[i]);


@@ -264,8 +255,8 @@ build_relations (void)
          while (!done)
            {
              done = true;
          while (!done)
            {
              done = true;

-             /* Each rhs ends in an item number, and there is a
-                sentinel before the first rhs, so it is safe to
+             /* Each rhs ends in a rule number, and there is a
+                sentinel (ritem[-1]=0) before the first rhs, so it is safe to

                 decrement RP here.  */
              rp--;
              if (ISVAR (*rp))
                 decrement RP here.  */
              rp--;
              if (ISVAR (*rp))


@@ -304,7 +295,7 @@ compute_FOLLOWS (void)
 {
   goto_number i;
 
 {
   goto_number i;
 

-  relation_digraph (includes, ngotos, &F);
+  relation_digraph (includes, ngotos, &goto_follows);

 
   for (i = 0; i < ngotos; i++)
     free (includes[i]);
 
   for (i = 0; i < ngotos; i++)
     free (includes[i]);


@@ -321,14 +312,13 @@ compute_lookahead_tokens (void)
 
   for (i = 0; i < nLA; i++)
     for (sp = lookback[i]; sp; sp = sp->next)
 
   for (i = 0; i < nLA; i++)
     for (sp = lookback[i]; sp; sp = sp->next)

-      bitset_or (LA[i], LA[i], F[sp->value]);
+      bitset_or (LA[i], LA[i], goto_follows[sp->value]);

 
   /* Free LOOKBACK. */
   for (i = 0; i < nLA; i++)
     LIST_FREE (goto_list, lookback[i]);
 
   free (lookback);
 
   /* Free LOOKBACK. */
   for (i = 0; i < nLA; i++)
     LIST_FREE (goto_list, lookback[i]);
 
   free (lookback);

-  bitsetv_free (F);

 }
 
 
 }
 
 


@@ -338,31 +328,35 @@ compute_lookahead_tokens (void)
 `----------------------------------------------------*/
 
 static int
 `----------------------------------------------------*/
 
 static int

-state_lookahead_tokens_count (state *s)
+state_lookahead_tokens_count (state *s, bool default_reduction_only_for_accept)

 {
 {

-  int k;

   int n_lookahead_tokens = 0;
   reductions *rp = s->reductions;
   transitions *sp = s->transitions;
 
   int n_lookahead_tokens = 0;
   reductions *rp = s->reductions;
   transitions *sp = s->transitions;
 

-  /* We need a lookahead either to distinguish different
-     reductions (i.e., there are two or more), or to distinguish a
-     reduction from a shift.  Otherwise, it is straightforward,
-     and the state is `consistent'.  */
+  /* Transitions are only disabled during conflict resolution, and that
+     hasn't happened yet, so there should be no need to check that
+     transition 0 hasn't been disabled before checking if it is a shift.
+     However, this check was performed at one time, so we leave it as an
+     aver.  */
+  aver (sp->num == 0 || !TRANSITION_IS_DISABLED (sp, 0));
+
+  /* We need a lookahead either to distinguish different reductions
+     (i.e., there are two or more), or to distinguish a reduction from a
+     shift.  Otherwise, it is straightforward, and the state is
+     `consistent'.  However, do not treat a state with any reductions as
+     consistent unless it is the accepting state (because there is never
+     a lookahead token that makes sense there, and so no lookahead token
+     should be read) if the user has otherwise disabled default
+     reductions.  */

   if (rp->num > 1
   if (rp->num > 1

-      || (rp->num == 1 && sp->num &&
-         !TRANSITION_IS_DISABLED (sp, 0) && TRANSITION_IS_SHIFT (sp, 0)))
+      || (rp->num == 1 && sp->num && TRANSITION_IS_SHIFT (sp, 0))
+      || (rp->num == 1 && rp->rules[0]->number != 0
+          && default_reduction_only_for_accept))

     n_lookahead_tokens += rp->num;
   else
     s->consistent = 1;
 
     n_lookahead_tokens += rp->num;
   else
     s->consistent = 1;
 

-  for (k = 0; k < sp->num; k++)
-    if (!TRANSITION_IS_DISABLED (sp, k) && TRANSITION_IS_ERROR (sp, k))
-      {
-       s->consistent = 0;
-       break;
-      }
-

   return n_lookahead_tokens;
 }
 
   return n_lookahead_tokens;
 }
 


@@ -371,28 +365,39 @@ state_lookahead_tokens_count (state *s)
 | Compute LA, NLA, and the lookahead_tokens members.  |
 `----------------------------------------------------*/
 
 | Compute LA, NLA, and the lookahead_tokens members.  |
 `----------------------------------------------------*/
 

-static void
+void

 initialize_LA (void)
 {
   state_number i;
   bitsetv pLA;
 initialize_LA (void)
 {
   state_number i;
   bitsetv pLA;

+  bool default_reduction_only_for_accept;
+  {
+    char *default_reductions =
+      muscle_percent_define_get ("lr.default-reductions");
+    default_reduction_only_for_accept =
+      0 == strcmp (default_reductions, "accepting");
+    free (default_reductions);
+  }

 
   /* Compute the total number of reductions requiring a lookahead.  */
   nLA = 0;
   for (i = 0; i < nstates; i++)
 
   /* Compute the total number of reductions requiring a lookahead.  */
   nLA = 0;
   for (i = 0; i < nstates; i++)

-    nLA += state_lookahead_tokens_count (states[i]);
+    nLA +=
+      state_lookahead_tokens_count (states[i],
+                                    default_reduction_only_for_accept);

   /* Avoid having to special case 0.  */
   if (!nLA)
     nLA = 1;
 
   pLA = LA = bitsetv_create (nLA, ntokens, BITSET_FIXED);
   /* Avoid having to special case 0.  */
   if (!nLA)
     nLA = 1;
 
   pLA = LA = bitsetv_create (nLA, ntokens, BITSET_FIXED);

-  lookback = xcalloc (nLA, sizeof *lookback);

 
   /* Initialize the members LOOKAHEAD_TOKENS for each state whose reductions
      require lookahead tokens.  */
   for (i = 0; i < nstates; i++)
     {
 
   /* Initialize the members LOOKAHEAD_TOKENS for each state whose reductions
      require lookahead tokens.  */
   for (i = 0; i < nstates; i++)
     {

-      int count = state_lookahead_tokens_count (states[i]);
+      int count =
+        state_lookahead_tokens_count (states[i],
+                                      default_reduction_only_for_accept);

       if (count)
        {
          states[i]->reductions->lookahead_tokens = pLA;
       if (count)
        {
          states[i]->reductions->lookahead_tokens = pLA;


@@ -444,6 +449,7 @@ lalr (void)
   initialize_LA ();
   set_goto_map ();
   initialize_F ();
   initialize_LA ();
   set_goto_map ();
   initialize_F ();

+  lookback = xcalloc (nLA, sizeof *lookback);

   build_relations ();
   compute_FOLLOWS ();
   compute_lookahead_tokens ();
   build_relations ();
   compute_FOLLOWS ();
   compute_lookahead_tokens ();


@@ -459,22 +465,25 @@ lalr_update_state_numbers (state_number old_to_new[], state_number nstates_old)
   goto_number ngotos_reachable = 0;
   symbol_number nonterminal = 0;
   aver (nsyms == nvars + ntokens);
   goto_number ngotos_reachable = 0;
   symbol_number nonterminal = 0;
   aver (nsyms == nvars + ntokens);

-  for (goto_number i = 0; i < ngotos; ++i)
-    {
-      while (i == goto_map[nonterminal])
-        goto_map[nonterminal++] = ngotos_reachable;
-      /* If old_to_new[from_state[i]] = nstates_old, remove this goto
-         entry.  */
-      if (old_to_new[from_state[i]] != nstates_old)
-        {
-          /* from_state[i] is not removed, so it and thus to_state[i] are
-             reachable, so to_state[i] != nstates_old.  */
-          aver (old_to_new[to_state[i]] != nstates_old);
-          from_state[ngotos_reachable] = old_to_new[from_state[i]];
-          to_state[ngotos_reachable] = old_to_new[to_state[i]];
-          ++ngotos_reachable;
-        }
-    }
+  {
+    goto_number i;
+    for (i = 0; i < ngotos; ++i)
+      {
+        while (i == goto_map[nonterminal])
+          goto_map[nonterminal++] = ngotos_reachable;
+        /* If old_to_new[from_state[i]] = nstates_old, remove this goto
+           entry.  */
+        if (old_to_new[from_state[i]] != nstates_old)
+          {
+            /* from_state[i] is not removed, so it and thus to_state[i] are
+               reachable, so to_state[i] != nstates_old.  */
+            aver (old_to_new[to_state[i]] != nstates_old);
+            from_state[ngotos_reachable] = old_to_new[from_state[i]];
+            to_state[ngotos_reachable] = old_to_new[to_state[i]];
+            ++ngotos_reachable;
+          }
+      }
+  }

   while (nonterminal <= nvars)
     {
       aver (ngotos == goto_map[nonterminal]);
   while (nonterminal <= nvars)
     {
       aver (ngotos == goto_map[nonterminal]);